Seat back frame

This application claims priority to Japanese patent application serial number 2012-140301, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a seat back frame of a vehicle seat.

2. Description of the Related Art

The vehicle seat has a seat back. A seat back described in Japanese Laid-Open Patent Publication 2008-194289 has a seat back main body adapted to support a back of an occupant, and an extension portion extending from a side of the seat back main body. The seat back main body has a main body frame having high structural strength and it's preferably fixed onto a floor. The extension portion has an extension frame supported on the side of the main body frame in a cantilever-like manner. The extension frame and the main body frame each have a circular pipe, and the extension frame and the main body frame are connected to each other by a connection structure. The connection structure has a steel bracket that connects the circular pipes. The bracket extends behind the circular pipes to contact rear sides of the circular pipes. While the connection structure may be resistant to forces approaching the extension portion from the front, it is vulnerable to forces approaching from the rear.

Therefore, there is a need in the art for a seat back frame that has an extension portion with high structural strength.

SUMMARY OF THE INVENTION

According to an aspect of the invention, certain embodiments of the present invention include a seat back frame of a vehicle seat. The vehicle seat has a seat back main body configured to support a back of an occupant and an extension portion extending from a side of the seat back main body. The seat back frame has a main body frame, an extension frame, and a connection member. The main body frame may form a framework for the seat back main body and may be mounted on a base. The extension frame may form a framework of the extension portion. The connection member connects the extension frame to a side of the main body frame. The seat back frame further has a rear support portion and a front support portion. The rear support portion contacts the main body frame and the extension frame from the rear so that the rear support portion integrally couples the main body frame with the extension frame. The front support portion contacts the main body frame and the extension frame from the front so that the front support portion integrally couples the main body frame to the extension frame.

Thus, the extension frame is supported and connected from both the front and rear sides with respect to the main body frame. Thereby, the seat back frame can have a connection structure that is resistant to forces coming from both the front and the rear. The strength of the extension portion can be increased by the connection structure.

In another aspect of the invention, the rear and front support portions may be provided at different heights. In this configuration, a bent portion or a protrusion portion extending in a front-back direction may be used for the rear and front support portions so that they won't interfere with each other. Thus, it is possible to reduce the thickness in the front-back direction of the seat back frame.

In another aspect of the invention the rear support portion may be configured so as to connect an upper portion of the main body frame and an upper portion of the extension frame. The front support portion may be configured so as to connect an intermediate portion of the main body frame and an intermediate portion of the extension frame. Force coming from the front side of the seat may be transferred to the extension portion. This force may then be substantially transferred at a location from the front support portion to the seat back main body. This location of transfer may be lower than the position of a rear support portion. In this way, the structural strength of the extension portion can be effectively increased.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of a seat with a seat back frame of one aspect of the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> is a perspective view of the seat back frame;

<figref idref="DRAWINGS">FIG. 3</figref> is a rear view of the seat back frame; and

<figref idref="DRAWINGS">FIG. 4</figref> is an enlarged perspective view of a main portion of the seat back frame shown from behind.

DETAILED DESCRIPTION OF THE INVENTION

Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved seat back frames. Representative examples of the present invention, which utilize many of these additional features and teachings both separately and in conjunction with one another, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of ordinary skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Moreover, various features of the representative examples and the dependent claims may be combined in ways that are not specifically enumerated in order to provide additional useful configurations of the present teachings.

A vehicle seat <b>1</b> shown in <figref idref="DRAWINGS">FIG. 1</figref> is a driver's seat of a vehicle. The vehicle seat <b>1</b> has a seat back <b>2</b> that supports a back of an occupant sitting on the vehicle seat <b>1</b>, a seat cushion <b>3</b> on which the occupant sits, and a headrest <b>4</b> that supports a head of the occupant. The seat back <b>2</b> has a seat back frame <b>10</b>.

The seat back <b>2</b> has a seat back main body <b>2</b>A that supports the back of the occupant, and an extension portion <b>2</b>B that extends to the inside of the vehicle (a right side as shown in <figref idref="DRAWINGS">FIG. 1</figref>) from the seat back main body <b>2</b>A. The extension portion <b>2</b>B extends laterally from the seat back main body <b>2</b>A. The extension portion <b>2</b>B preferably has a surface located on the same plane as a surface of the seat back main body <b>2</b>A, and a back surface located on the same plane as a back surface of the seat back main body <b>2</b>A. The extension portion <b>2</b>B preferably has the same side shape as a side shape of the seat back main body <b>2</b>A. That is to say, the shape of a projection side of the extension portion <b>2</b>B may be substantially the same as the shape of a projection side of the seat back main body <b>2</b>A. A seat back of a passenger seat (not shown) is located near the lateral side of the seat back main body <b>2</b>A. The extension portion <b>2</b>B is able to connect the seat back main body <b>2</b>A and the seat back of the passenger seat.

The seat back main body <b>2</b>A and the seat cushion <b>3</b> may be connected to each other by a disk-shaped reclining device <b>5</b>. The reclining device <b>5</b> is a rotary shaft device that can connect the two members such that they can rotate and/or be arranged in a fixed manner. The reclining device <b>5</b> connects the lower end portions of both the left and right sides of the seat back main body <b>2</b>A and the rear end portions of both the left and right sides of the seat cushion <b>3</b>. The reclining device <b>5</b> connects the lower end portions of both side frames <b>11</b> of the seat back main body <b>2</b>A and the rear end portions of both side frames <b>3</b>A of the seat cushion <b>3</b>. Thereby, a backrest angle of the seat back <b>2</b> relative to the seat cushion <b>3</b> can be adjusted.

Each of the reclining devices <b>5</b> is usually maintained in a locked state whereby they fix the backrest angle of the seat back <b>2</b>. A release lever <b>5</b>C is provided on an outer side (a left side in a show direction) of the seat cushion <b>3</b>. When the release lever <b>5</b>C is pulled up, the reclining device <b>5</b> is unlocked. The reclining device <b>5</b> has an operation shaft <b>5</b>A inserted into the center thereof. The operation shafts <b>5</b>A of a pair of reclining devices <b>5</b> are connected by a connecting rod <b>5</b>B and can be rotated. When the release lever <b>5</b>C is pulled up, the operation shaft <b>5</b>A located on an outer side is rotated in the release operation direction. The operation shaft <b>5</b>A of the inner side is also rotated in the release operation direction at the same time. In this way, both of the reclining devices <b>5</b> can be unlocked at the same time.

Each of the reclining devices <b>5</b> switches from a locked state to an unlocked state whereby the backrest angle of the seat back <b>2</b> can be freely changed in the front-back direction. After changing the backrest angle of the seat back <b>2</b> to a predetermined angle, the operation of the release lever <b>5</b>C can be stopped. Thereby, each of the reclining devices <b>5</b> returns to the locked state again, and the backrest angle of the seat back <b>2</b> is fixed at the predetermined angle. The reclining device <b>5</b> can have the same configuration as that disclosed in the document of Japanese Laid-Open Patent Publication 2011-116303 or the like.

Between the left and right portions of the seat back <b>2</b> and the left and right portions of the seat cushion <b>3</b>, a spiral spring <b>6</b> is provided which typically biases the seat back <b>2</b> forward. When the fixation of the backrest angle of the seat back <b>2</b> is released, the seat back <b>2</b> rotates whereby it may come into contact with the back of the occupant via the biasing force of the spiral spring <b>6</b>. When the back of the occupant is tilted forwards or backwards, the backrest angle of the seat back <b>2</b> is changed in accordance with the tilting of the back. In this way, the backrest angle of the seat back <b>2</b> can be easily adjusted.

The seat cushion <b>3</b> may be provided on a floor of a vehicle using left and right slide devices (not shown). The position of the seat cushion <b>3</b> can be adjusted with respect to the floor in the front-back direction. The slide device can have, for example, a structure disclosed in the document of Japanese Laid-Open Patent Publication 2010-221935 or the like. The seat back <b>2</b> may have an extension portion <b>2</b>B. The seat cushion <b>3</b> may have an extension portion <b>3</b>B extending the seat width direction in accordance with the extension portion <b>2</b>B. On the upper surface of the extension portion <b>3</b>B, a recessed cup holder <b>3</b>C may be formed in which a drink or a small object can be placed.

The headrest <b>4</b> is typically mounted above the seat back <b>2</b>. The headrest <b>4</b> preferably has two rod-like stays (not shown) protruding downward from the headrest main body. The seat back frame <b>10</b> of the seat back <b>2</b> has an upper frame <b>12</b>. The two square tube-shaped holders <b>15</b> may be fixed to the upper frame <b>12</b>. A support member may be mounted inside each of the holders <b>15</b>. The stays may be inserted into the support members, and the headrest <b>4</b> may be fixed to the upper portion of the seat back <b>2</b>. The mounting structure, which mounts the headrest <b>4</b> to the seat back <b>2</b>, can have a structure, for example, disclosed in Japanese Laid-Open Patent Publication 2008-239075.

As shown in <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, the seat back frame <b>10</b> has a main body frame <b>10</b>A, an extension frame <b>10</b>B, and a connection member <b>16</b>. The main body frame <b>10</b>A forms a a framework of the seat back main body <b>2</b>A. The extension frame <b>10</b>B forms a framework of the extension portion <b>2</b>B. The connection member <b>16</b> connects the extension frame <b>10</b>B to the main body frame <b>10</b>A.

The main body frame <b>10</b>A has side frames <b>11</b>, upper frame <b>12</b>, holders <b>15</b>, an upper reinforcement plate <b>13</b>, and a lower reinforcement plate <b>14</b>. The components are integrally assembled. The side frame <b>11</b> has a pair of vertical left and right plates. The upper frame <b>12</b> is an inverse U-shaped pipe that connects the upper end portions of the side frames <b>11</b>. The holder <b>15</b> has a square tube shape, and is provided on the left and right portions of the upper frame <b>12</b>. The upper reinforcement plate <b>13</b> has a horizontal plate between the left and right leg portions of the upper frame <b>12</b>. The lower reinforcement plate <b>14</b> has a horizontal plate between the lower portions of the side frames <b>11</b>.

When manufacturing the side frame <b>11</b>, a steel plate material is cut in a vertically long shape using a press. Next, the front and rear edge portions of the steel plate material are bent to the inside of the seat in a flange shape. Each of the bent edge portions is able to increase strength resistant to bending or distortion of the side frame <b>11</b>. Each of the edge portions suppresses the protrusion of the side frame <b>11</b> to the outside (the front and the rear or the outside of the seat). The side frame <b>11</b> is located on the side of the seat back main body <b>2</b>A, and forms the framework of both of left and right sides of the seat back main body <b>2</b>A. Both of the side frames <b>11</b> have the surfaces facing each other in the seat width direction.

When manufacturing the upper frame <b>12</b>, a circular steel pipe is typically cut to a predetermined length using a press. Next, the circular steel pipe material is bent in an inverse U shape. The upper frame <b>12</b> has left and right leg portions extending downward, and both of the leg portions are welded to the upper end portion of each of the side frames <b>11</b>. In this way, the upper frame <b>12</b> can be coupled to the side frame <b>11</b>.

The upper end portion of the side frame <b>11</b> is bent in a semi-cylindrical shape so that the shape thereof is matched with the outer circumferential surface of each leg portion of the upper frame <b>12</b>. Thereby, each leg portion of the upper frame <b>12</b> can contact with each upper end portion of each side frame <b>11</b> in a wide area. They are typically can be welded in a wide area and coupled to each other.

The holder <b>15</b> is manufactured by cutting a squared-off steel pipe to a predetermined length. The holder <b>15</b> extends vertically. The upper portion of the holder <b>15</b> is connected to a front surface of a central portion extending in the seat width direction of the upper frame <b>12</b>. The lower portion of the holder <b>15</b> is connected to a front surface of the upper reinforcement plate <b>13</b> by the welding. The holder <b>15</b> can support the headrest <b>4</b> (see <figref idref="DRAWINGS">FIG. 1</figref>) due to its high structural strength. It uses the upper frame <b>12</b> and the upper reinforcement plate <b>13</b> for support.

When manufacturing the upper reinforcement plate <b>13</b>, a sheet of steel material is cut using a press. Next, the upper and lower edge portions of the steel material are bent to the front of the seat in a flange shape. The upper and lower bent edge portions can increase strength resistance to bending or distortion. The upper and lower edge portions can suppress the angulation of the upper reinforcement plate <b>13</b> to the outside (the rear side of the seat). The left and right end portions of the upper reinforcement plate <b>13</b> are welded to the rear surfaces of each leg portion of the upper frame <b>12</b>. In this way, the upper reinforcement plate <b>13</b> can be fixed and integrally coupled to both leg portions of the upper frame <b>12</b>. Each end portion of the upper reinforcement plate <b>13</b> is bent in a semi-cylindrical shape that is matched with the outer circumferential surface of the leg portions of the upper frame <b>12</b>. Thereby, each end portion of the upper reinforcement plate <b>13</b> can contact each leg portion of the upper frame <b>12</b>. They are preferably welded and coupled to each other.

In manufacturing the lower reinforcement plate <b>14</b>, a sheet of steel is cut using a press. Next, the upper and lower edge portions of the steel plate material are bent to the front of the seat in a flange shape. The upper and lower edge portions can increase strength resistant to bending or distortion of the lower reinforcement plate <b>14</b>. The upper and lower edge portions can suppress the angulation of the lower reinforcement plate <b>14</b> to the outside (the rear side of the seat). The left and right end portions of the lower reinforcement plate <b>14</b> are welded to a front surface of the rear edge portion bend to the inside of the seat of the lower portion of the side frame <b>11</b>. Thereby, the lower reinforcement plate <b>14</b> can be coupled to the lower portions of the side frames <b>11</b>.

When manufacturing the extension frame <b>10</b>B, in the same manner as the upper frame <b>12</b>, a steel pipe is cut to a predetermined length. Next, the steel pipe is bent in a U shape in the transverse direction. The extension frame <b>10</b>B is placed so that the U-shaped opening faces the main body frame <b>10</b>A. The upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B is coupled to a shoulder portion of the upper frame <b>12</b> of the main body frame <b>10</b>A by a rear support member (portion) <b>16</b>A of the connection member <b>16</b>. A lower end portion <b>10</b>B<b>2</b> penetrates and is fitted to the side frame <b>11</b> of the main body frame <b>10</b>A, and is coupled to the side frame <b>11</b> by welding.

The extension frame <b>10</b>B has an intermediate portion <b>10</b>B<b>3</b> extending vertically and downward from the upper end portion <b>10</b>B<b>1</b> to the lower end portion <b>10</b>B<b>2</b>. The intermediate portion <b>10</b>B<b>3</b> is coupled to a leg portion (a portion <b>12</b>B) of the upper frame <b>12</b> of the main body frame <b>10</b>A by a front support member (portion) <b>16</b>B of the connection member <b>16</b>. One side of the extension frame <b>10</b>B is coupled to the main body frame <b>10</b>A, and the extension frame <b>10</b>B is supported by the main body frame <b>10</b>A. The extension frame <b>10</b>B is at least partially provided within the main body frame <b>10</b>A, and extends from the main body frame <b>10</b>A in the lateral direction.

The lower end portion <b>10</b>B<b>2</b> of the extension frame <b>10</b>B is fitted to a circular hole formed in the side frame <b>11</b> in the seat width direction, and is welded to the side frame <b>11</b>. For that reason, the extension frame <b>10</b>B can be coupled to the main body frame <b>10</b>A in a simple configuration. However, the upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B is coupled to the upper frame <b>12</b>, without being fitted to the through hole of the upper frame <b>12</b>. For that reason, the extension frame <b>10</b>B is not coupled to the main body frame <b>10</b>A in a simple configuration. The upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B is coupled to the shoulder portion of the upper frame <b>12</b> formed by bending of the circular steel pipe. They are preferably connected via the connection member <b>16</b>. The connection member <b>16</b> fixedly and integrally couples the extension frame <b>10</b>B with the upper frame <b>12</b> through a relatively simple configuration, without lowering the structural strength of the main body frame <b>10</b>A.

As shown in <figref idref="DRAWINGS">FIGS. 2 to 4</figref>, the connection member <b>16</b> has a rear support member <b>16</b>A and a front support member <b>16</b>B. The rear support member <b>16</b>A is a flat plate-shaped steel plate material. The rear support member <b>16</b>A is coupled to the rear surface of the upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B and the rear surface of the shoulder portion of the upper frame <b>12</b>. The front support member <b>16</b>B is a circular steel pipe material. The front support member <b>16</b>B is coupled to the front surface of the intermediate portion <b>10</b>B<b>3</b> of the extension frame <b>10</b>B and the front surface of the leg portion (the portion <b>12</b>B) of the upper frame <b>12</b>. In this way, the rear support member <b>16</b>A and the front support member <b>16</b>B couple the extension frame <b>10</b>B to the upper frame <b>12</b>.

As shown in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>, the rear support member <b>16</b>A is coupled with the rear surface of the upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B and the rear surface of the first portion <b>12</b>A and the rear surface of the second portion <b>12</b>B of the upper frame <b>12</b>. The rear support member <b>16</b>A is coupled to each of three back surfaces through welding. The upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B extends in the seat width direction. The first portion <b>12</b>A extends in the seat width direction of the shoulder portion of the upper frame <b>12</b>. The second portion <b>12</b>B is bent and extends downward from the first portion <b>12</b>A.

The rear support member <b>16</b>A is coupled to the rear surface of the second portion <b>12</b>B, and thus the rotation about the first portion <b>12</b>A is restricted. The rear support member <b>16</b>A is coupled to the rear surface of the upper end portion <b>10</b>B<b>1</b> and the rear surface of the first portion <b>12</b>A. In this way, the rotation about the second portion <b>12</b>B is restricted. The rear support member <b>16</b>A can be coupled to both the first portion <b>12</b>A and the second portion <b>12</b>B.

The rear support member <b>16</b>A is provided in the shoulder portion of the upper frame <b>12</b>, and the upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B is coupled to the rear support member <b>16</b>A. Thus, the rear support member <b>16</b>A is able to couple the extension frame <b>10</b>B to the shoulder portion of the upper frame <b>12</b>.

The rear support member <b>16</b>A has a pair of semi-cylindrical upper edge portions <b>16</b>A<b>1</b>. One upper edge portion <b>16</b>A<b>1</b> contacts the first portion <b>12</b>A of the upper frame <b>12</b>, and corresponds to an outer circumferential surface shape of the steel pipe of the first portion <b>12</b>A. The other upper edge portion <b>16</b>A<b>1</b> contacts the extension frame <b>10</b>B, and corresponds to the outer circumferential surface shape of the steel pipe of the extension frame <b>10</b>B. Each of the upper edge portions <b>16</b>A<b>1</b> can contact the first portion <b>12</b>A and the extension frame <b>10</b>B, and can be welded to it. Thereby, the rear support member <b>16</b>A can be coupled to the first portion <b>12</b>A and the extension frame <b>10</b>B.

The upper edge portions <b>16</b>A<b>1</b> has a semi-cylindrical shape that extends from the rear of the frames to the front so as to be able to contact the first portion <b>12</b>A of the upper frame <b>12</b> and the extension frame <b>10</b>B. In this way, the rear support member <b>16</b>A can contact the first portion <b>12</b>A and the extension frame <b>10</b>B from both the front and the rear.

The front support member <b>16</b>B is a steel pipe. Both end portions <b>16</b>B<b>1</b> of the front support member <b>16</b>B have a crushed flat shape. The both end portions <b>16</b>B<b>1</b> contact the intermediate portion <b>10</b>B<b>3</b> of the extension frame <b>10</b>B and the second portion <b>12</b>B of the upper frame <b>12</b> from the front, and are welded thereto. In this way, the front support member <b>16</b>B is coupled to the extension frame <b>10</b>B and the upper frame <b>12</b>.

The front support member <b>16</b>B has a central portion having a steel pipe-shape. The central portion extends in the seat width direction. The central portion is perpendicular to the intermediate portion <b>10</b>B<b>3</b> of the extension frame <b>10</b>B and the second portion <b>12</b>B of the upper frame <b>12</b>. The central portion is located in the front-back direction in substantially the same manner as the intermediate portion <b>10</b>B<b>3</b> and the second portion <b>12</b>B. Both end portions <b>16</b>B<b>1</b> of the front support member <b>16</b>B have a crushed and curved shape so as to correspond to the shapes of the front surfaces of the intermediate portion <b>10</b>B<b>3</b> and the second portion <b>12</b>B. Thereby, both end portions <b>16</b>B<b>1</b> can contact the intermediate portion <b>10</b>B<b>3</b> and the second portion <b>12</b>B and be welded thereto. Thereby, the front support member <b>16</b>B is coupled to the intermediate portion <b>10</b>B<b>3</b> and the second portion <b>12</b>B.

The front support member <b>16</b>B is set to substantially the same height as the upper reinforcement plate <b>13</b>. The upper reinforcement plate <b>13</b> is welded to the rear surface of both leg portions of the upper frame <b>12</b>. The upper reinforcement plate <b>13</b> supports the main body frame <b>10</b>A from the rear. The front support member <b>16</b>B supports the extension frame <b>10</b>B from the front. Thus, the main body frame <b>10</b>A and the extension frame <b>10</b>B are fixedly supported by each other, and thus are hard to deflect or twist in the front-back direction.

The rear support member <b>16</b>A and the front support member <b>16</b>B support and connect the extension frame <b>10</b>B and the main body frame <b>10</b>A from the front-back direction. Thus, the extension frame <b>10</b>B is resistant to the input load from both sides of the front and back with respect to the main body frame <b>10</b>A. For example, when the seat back <b>2</b> is stood up, the extension frame <b>10</b>B can sufficiently resist forces that may be transmitted to the extension portion <b>2</b>B from the front or the rear. When the seat back <b>2</b> is brought down forward, the extension frame <b>10</b>B can sufficiently resist forces that may be transmitted to the back surface of the extension portion <b>2</b>B from above.

The rear support member <b>16</b>A and the front support member <b>16</b>B are located at different positions. For that reason, the rear support member <b>16</b>A can contact the upper edge portion <b>16</b>A<b>1</b> without interfering with the front support member <b>16</b>B. The front support member <b>16</b>B can be placed at the front-back position corresponding to the upper frame <b>12</b> and the extension frame <b>10</b>B without interfering with the rear support member <b>16</b>A. Thus, the thickness in the front-back direction of the seat back frame <b>10</b> can be reduced.

The rear support member <b>16</b>A is provided at the high position in which the shoulder portion of the upper frame <b>12</b> and the upper end portion <b>10</b>B<b>1</b> of the extension frame <b>10</b>B are connected to each other. The front support member <b>16</b>B is provided at the low position in which the second portion <b>12</b>B of the upper frame <b>12</b> and the intermediate portion <b>10</b>B<b>3</b> of the extension frame <b>10</b>B are connected to each other. Thus, the load applied to the extension portion <b>2</b>B from the seat front is transmitted to the seat back main body <b>2</b>A by the front support member <b>16</b>B at the low position compared to the rear support member <b>16</b>A. Thus, the structural strength of the extension portion <b>2</b>B can be effectively increased.

While the embodiments of invention have been described with reference to specific configurations, it will be apparent to those skilled in the art that many alternatives, modifications and variations may be made without departing from the scope of the present invention. Accordingly, embodiments of the present invention are intended to embrace all such alternatives, modifications and variations that may fall within the spirit and scope of the appended claims. For example, embodiments of the present invention should not be limited to the representative configurations, but may be modified, for example, as described below.

The seat back frame may be applied to the seat back of the driver's seat as described above, and may be applied to the seat backs of other seats. The seat back frame may be applied to the seats of the vehicle such as a car, and may be applied to, for example, vehicles such as a railway vehicle.

As described above, the extension portion can be located between the seats positioned adjacent to each other. The extension portion connects the seat backs of the seats so as to fill the space between the seat backs. Alternatively or additionally, the extension portion may support the back of the occupant sitting in front of the extension portion.

The extension frame and the main body frame (the upper frame) each may be the circular steel pipe as described above. Alternatively, the extension frame may be a steel pipe, a squared-off steel pipe or the like.

The rear support member and the front support member may be configured as described above and may have other structures. As described above, the rear support member and the front support member may be different members. Alternatively, both the rear support portion (member) and the front support portion (member) may be constructed as a single member.

The rear and front support members may be welded and coupled to the main body frame or the extension frame as described above. Alternatively, the rear and front support members may be coupled to the main body frame or the extension frame by a bolt, caulking or the like.

As described above, the rear and front support members may be set to heights different from each other. Alternatively, the rear and front support members may be set at the same height.

The rear support member may be located above the front support member as described above. Alternatively, the rear support member may be located below the front support member.

As described above, the main body frame of the seat back main body may be connected to the seat cushion so as to be capable of reclining. Alternatively, the main body frame may be fixed to the seat cushion. Alternatively, the main body frame may be fixed to a base member fixed on the floor. Alternatively, the main body frame may be fixed to a member fixed on the floor or may be attached to the member capable for reclining.

As described above, the main body frame of the seat back main body may be connected to the floor via the seat cushion <b>3</b>. Alternatively, the main body frame may be directly connected to the floor (base).

As described above, the main body frame of the seat back main body is connected to a base. The base may be floor described above, a side panel, a roof panel, a vehicle member, a part of a vehicle body, or the like.

As described above, the seat back frame may comprise one rear support member and one front support member. Alternatively, the seat back frame may more than one rear support members and/or more than one front support members. All of the rear support members may be provided at a first height or first heights. All of the front support portions may be provided at a second height or second heights. All of the second heights may be different heights from all of the first height or first heights.

As described above, the upper reinforcement plate <b>13</b> and the front support member (portion) <b>16</b>B may be the different members. Alternatively, the upper reinforcement plate <b>13</b> and the front support member (portion) <b>16</b>B may be constructed by or formed of one member.